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A poor maternal diet during pregnancy predisposes the infant to severe lower respiratory tract infections (sLRIs), which, in turn, increases childhood asthma risk; however, the underlying mechanisms remain poorly understood. Here, we show that the offspring of high-fat diet (HFD)-fed mothers (HFD-reared pups) developed an sLRI following pneumovirus inoculation in early life and subsequent asthma in later life upon allergen exposure. Prior to infection, HFD-reared pups developed microbial dysbiosis and low-grade systemic inflammation (LGSI), characterized by hyperneutropoiesis in the liver and elevated inflammatory cytokine expression, most notably granulocyte-colony stimulating factor (G-CSF), interleukin-17A (IL-17A), IL-6 and soluble IL-6 receptor (sIL-6R) (indicative of IL-6 trans-signaling) in the circulation and multiple organs but most prominently the liver. Inhibition of IL-6 trans-signaling using sgp130Fc transgenic mice or via specific genetic deletion of IL-6Ra on neutrophils conferred protection against both diseases. Taken together, our findings suggest that a maternal HFD induces neonatal LGSI that predisposes to sLRI and subsequent asthma via neutrophil-mediated IL-6 trans-signaling., Competing Interests: Declaration of interests S.R.-J. has acted as a consultant for AbbVie, Chugai, Roche, Regeneron, Genentech Roche, Pfizer, Sanofi, and I-Mab Biopharma regarding the use of interleukin-6 blockade with other agents. He is a member of the supervisory board of the CONARIS Research Institute. He also declares that he is an inventor on patents owned by CONARIS Research Institute, which develops the sgp130Fc protein olamkicept together with Ferring Pharmaceuticals and I-Mab Biopharma. S.R.-J. has stock ownership in CONARIS. G.A.R. is a member of the board of genomiQa., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Abstract: Autophagy is an intracellular survival process that has established roles in the long-term survival and function of hematopoietic stem cells (HSC). We investigated the contribution of autophagy to HSC fitness during allogeneic transplantation and graft-versus-host disease (GVHD). We demonstrate in vitro that both tumor necrosis factor and IL-1β, major components of GVHD cytokine storm, synergistically promote autophagy in both HSC and their more mature hematopoietic progenitor cells (HPC). In vivo we demonstrate that autophagy is increased in donor HSC and HPC during GVHD. Competitive transplant experiments demonstrated that autophagy-deficient cells display reduced capacity to reconstitute the hematopoietic system compared to wild-type counterparts. In a major histocompatibility complex-mismatched model of GVHD and associated cytokine dysregulation, we demonstrate that autophagy-deficient HSC and progenitors fail to establish durable hematopoiesis, leading to primary graft failure and universal transplant related mortality. Using several different models, we confirm that autophagy activity is increased in early progenitor and HSC populations in the presence of T-cell-derived inflammatory cytokines and that these HSC populations require autophagy to survive. Thus, autophagy serves as a key survival mechanism in HSC and progenitor populations after allogeneic stem cell transplant and may represent a therapeutic target to prevent graft failure during GVHD., (© 2024 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Abstract: Chronic graft-versus-host disease (cGVHD) remains a significant complication of allogeneic hematopoietic stem cell transplantation. Central nervous system (CNS) involvement is becoming increasingly recognized, in which brain-infiltrating donor major histocompatibility complex (MHC) class II+ bone marrow-derived macrophages (BMDM) drive pathology. BMDM are also mediators of cutaneous and pulmonary cGVHD, and clinical trials assessing the efficacy of antibody blockade of colony-stimulating factor 1 receptor (CSF1R) to deplete macrophages are promising. We hypothesized that CSF1R antibody blockade may also be a useful strategy to prevent/treat CNS cGVHD. Increased blood-brain barrier permeability during acute GVHD (aGVHD) facilitated CNS antibody access and microglia depletion by anti-CSF1R treatment. However, CSF1R blockade early after transplant unexpectedly exacerbated aGVHD neuroinflammation. In established cGVHD, vascular changes and anti-CSF1R efficacy were more limited. Anti-CSF1R-treated mice retained donor BMDM, activated microglia, CD8+ and CD4+ T cells, and local cytokine expression in the brain. These findings were recapitulated in GVHD recipients, in which CSF1R was conditionally depleted in donor CX3CR1+ BMDM. Notably, inhibition of CSF1R signaling after transplant failed to reverse GVHD-induced behavioral changes. Moreover, we observed aberrant behavior in non-GVHD control recipients administered anti-CSF1R blocking antibody and naïve mice lacking CSF1R in CX3CR1+ cells, revealing a novel role for homeostatic microglia and indicating that ongoing clinical trials of CSF1R inhibition should assess neurological adverse events in patients. In contrast, transfer of Ifngr-/- grafts could reduce MHC class II+ BMDM infiltration, resulting in improved neurocognitive function. Our findings highlight unexpected neurological immune toxicity during CSF1R blockade and provide alternative targets for the treatment of cGVHD within the CNS., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Traumatic brain injury (TBI) results in prolonged and non-resolving activation of microglia. Forced turnover of these cells during the acute phase of TBI aids recovery, but the cell-intrinsic pathways that underpin the pro-repair phenotype of these repopulating microglia remain unclear. Here, we show that selective targeting of ROCK2 with the small molecule inhibitor KD025 impairs the proliferative response of microglia after TBI as well as during genetically induced turnover of microglia. KD025 treatment abolished the substantial neuroprotective and cognitive benefits conferred by repopulating microglia, preventing these cells from replenishing the depleted niche during the early critical time window post-injury. Delaying KD025 treatment to the subacute phase of TBI allowed microglial repopulation to occur, but this did not enhance the benefits conferred by repopulating microglia. Taken together, our data indicate that ROCK2 mediates neuronal survival and microglial population dynamics after TBI, including the emergence of repopulating microglia with a pro-repair phenotype., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: AZ, WC and MN are full-time employees of Graviton Bioscience Corporation,Graviton Bioscience B.V.,Amsterdam, Netherlands 1017 CG. The authors declare that they have no competing financial interests or personal relationships that influenced the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Chronic graft-versus-host disease (cGvHD) remains a prominent barrier to allogeneic hematopoietic stem cell transplantion as the leading cause of nonrelapse mortality and significant morbidity. Tremendous progress has been achieved in both the understanding of pathophysiology and the development of new therapies for cGvHD. Although our field has historically approached treatment from an empiric position, research performed at the bedside and bench has elucidated some of the complex pathophysiology of cGvHD. From the clinical perspective, there is significant variability of disease manifestations between individual patients, pointing to diverse biological underpinnings. Capitalizing on progress made to date, the field is now focused on establishing personalized approaches to treatment. The intent of this article is to concisely review recent knowledge gained and formulate a path toward patient-specific cGvHD therapy., (Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution.)

Damage to the gastrointestinal tract following allogeneic hematopoietic stem cell transplantation is a significant contributor to the severity and perpetuation of graft-versus-host disease. In preclinical models and clinical trials, we showed that infusing high numbers of regulatory T cells reduces graft-versus-host disease incidence. Despite no change in in vitro suppressive function, transfer of ex vivo expanded regulatory T cells transduced to overexpress G protein-coupled receptor 15 or C-C motif chemokine receptor 9, specific homing receptors for colon or small intestine, respectively, lessened graft-versus-host disease severity in mice. Increased regulatory T cell frequency and retention within the gastrointestinal tissues of mice that received gut homing T cells correlated with lower inflammation and gut damage early post-transplant, decreased graft-versus-host disease severity, and prolonged survival compared with those receiving control transduced regulatory T cells. These data provide evidence that enforced targeting of ex vivo expanded regulatory T cells to the gastrointestinal tract diminishes gut injury and is associated with decreased graft-versus-host disease severity., (Copyright © 2023 American Society of Transplantation & American Society of Transplant Surgeons. Published by Elsevier Inc. All rights reserved.)

Alloreactive and autoimmune responses after allogeneic hematopoietic cell transplantation can occur in nonclassical chronic graft-versus-host disease (chronic GVHD) tissues and organ systems or manifest in atypical ways in classical organs commonly affected by chronic GVHD. The National Institutes of Health (NIH) consensus projects were developed to improve understanding and classification of the clinical features and diagnostic criteria for chronic GVHD. Although still speculative whether atypical manifestations are entirely due to chronic GVHD, these manifestations remain poorly captured by the current NIH consensus project criteria. Examples include chronic GVHD impacting the hematopoietic system as immune mediated cytopenias, endothelial dysfunction, or as atypical features in the musculoskeletal system, central and peripheral nervous system, kidneys, and serous membranes. These purported chronic GVHD features may contribute significantly to patient morbidity and mortality. Most of the atypical chronic GVHD features have received little study, particularly within multi-institutional and prospective studies, limiting our understanding of their frequency, pathogenesis, and relation to chronic GVHD. This NIH consensus project task force report provides an update on what is known and not known about the atypical manifestations of chronic GVHD while outlining a research framework for future studies to be undertaken within the next 3 to 7 years. We also provide provisional diagnostic criteria for each atypical manifestation, along with practical investigation strategies for clinicians managing patients with atypical chronic GVHD features., Competing Interests: Declaration of Competing Interest G.D.E.C. received consultancy fees from Miltenyi Biotech. M.S. received consultancy fees from Chugai/Roche, Hexal/Sandoz, Gilead, AbbVie, Janssen-Cilag, Boehringer/Ingelheim, onkowissen.de, EUSA-Pharma, Novartis, AstraZeneca, Amgen, Medac, and Lilly, travel support from Chugai/Roche, Boehringer/Ingelheim, Celgene, Medac, UCB, Mylan, and honoraria from BMS, Novartis, AbbVie, AstraZeneca, Chugai/Roche, Janssen-Cilag, Gilead, Boehringer/Ingelheim. O.P. received honoraria or travel support from Astellas, Gilead, Jazz, MSD, Neovii Biotech, Novartis, Pfizer and Therakos, received research support from Gilead, Incyte, Jazz, Neovii Biotech and Takeda, and is a member of advisory boards to Jazz, Gilead, MSD, Omeros, Priothera, Shionogi and SOBI. BDS has received consultancy fees from Janssen, Legend Biotech, Kite/Gilead, Celgene, BMS, and Incyte, and is a member of advisory board to In8bio. W.T.K. received grant support and consulting fees from Biogen and NControl Therapeutics, Inc. M. B.-H. received speaker fees from Alexion and Sanofi and received a grant for an advanced training course from Norvatis. R.Z. received speaker fees from Novartis, Incyte and Mallinckrodt. K.A. received travel support from Alexion, Bayer, Biogenldec, MerckSerono, Novartis, Teva (until 2014) and received honoraria from Biogenldec. Y.I. served on advisory boards for Novartis, Janssen, and Meiji Seika Pharma. S.J.L. received consultant fees from Mallinckrodt, Equillium, Kadmon; research funding from Amgen, AstraZeneca, Incyte, Kadmon, Novartis, Pfizer, Syndax, Takeda; drug supply from Janssen; she is on an Incyte Steering Committee. S.P. received research support from the Center for Cancer Research at the National Cancer Institute through the National Institutes of Health Intramural Research Program, which includes Clinical Research Development Agreements with Celgene, Actelion, Eli Lilly, Pharmacyclics and Kadmon Corporation. D.W. received research grant support from Novartis and honoraria from Novartis, Mallinckrodt, Behring, Takeda, Neovii, Gilead and Pfizer., (Copyright © 2022 The American Society for Transplantation and Cellular Therapy. All rights reserved.)

Despite advances in the field, chronic graft-versus-host-disease (cGVHD) remains a leading cause of morbidity and mortality following allogenic hematopoietic stem cell transplant. Because treatment options remain limited, we tested efficacy of anticancer, chromatin-modifying enzyme inhibitors in a clinically relevant murine model of cGVHD with bronchiolitis obliterans (BO). We observed that the novel enhancer of zeste homolog 2 (EZH2) inhibitor JQ5 and the BET-bromodomain inhibitor JQ1 each improved pulmonary function; impaired the germinal center (GC) reaction, a prerequisite in cGVHD/BO pathogenesis; and JQ5 reduced EZH2-mediated H3K27me3 in donor T cells. Using conditional EZH2 knockout donor cells, we demonstrated that EZH2 is obligatory for the initiation of cGVHD/BO. In a sclerodermatous cGVHD model, JQ5 reduced the severity of cutaneous lesions. To determine how the 2 drugs could lead to the same physiological improvements while targeting unique epigenetic processes, we analyzed the transcriptomes of splenic GCB cells (GCBs) from transplanted mice treated with either drug. Multiple inflammatory and signaling pathways enriched in cGVHD/BO GCBs were reduced by each drug. GCBs from JQ5- but not JQ1-treated mice were enriched for proproliferative pathways also seen in GCBs from bone marrow-only transplanted mice, likely reflecting their underlying biology in the unperturbed state. In conjunction with in vivo data, these insights led us to conclude that epigenetic targeting of the GC is a viable clinical approach for the treatment of cGVHD, and that the EZH2 inhibitor JQ5 and the BET-bromodomain inhibitor JQ1 demonstrated clinical potential for EZH2i and BETi in patients with cGVHD/BO., (© 2022 by The American Society of Hematology.)

Resident and recruited macrophages control the development and proliferation of the liver. We have previously shown in multiple species that treatment with a macrophage colony stimulating factor (CSF1)-Fc fusion protein initiated hepatocyte proliferation and promoted repair in models of acute hepatic injury in mice. Here, we investigated the impact of CSF1-Fc on resolution of advanced fibrosis and liver regeneration, using a non-resolving toxin-induced model of chronic liver injury and fibrosis in C57BL/6J mice. Co-administration of CSF1-Fc with exposure to thioacetamide (TAA) exacerbated inflammation consistent with monocyte contributions to initiation of pathology. After removal of TAA, either acute or chronic CSF1-Fc treatment promoted liver growth, prevented progression and promoted resolution of fibrosis. Acute CSF1-Fc treatment was also anti-fibrotic and pro-regenerative in a model of partial hepatectomy in mice with established fibrosis. The beneficial impacts of CSF1-Fc treatment were associated with monocyte-macrophage recruitment and increased expression of remodelling enzymes and growth factors. These studies indicate that CSF1-dependent macrophages contribute to both initiation and resolution of fibrotic injury and that CSF1-Fc has therapeutic potential in human liver disease., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)

Graft-versus-host disease (GVHD) remains the leading cause of nonrelapse mortality after allogeneic stem cell transplantation for hematological malignancies. Manifestations of GVHD in the central nervous system (CNS) present as neurocognitive dysfunction in up to 60% of patients; however, the mechanisms driving chronic GVHD (cGVHD) in the CNS are yet to be elucidated. Our studies of murine cGVHD revealed behavioral deficits associated with broad neuroinflammation and persistent Ifng upregulation. By flow cytometry, we observed a proportional shift in the donor-derived T-cell population in the cGVHD brain from early CD8 dominance to later CD4 sequestration. RNA sequencing of the hippocampus identified perturbations to structural and functional synapse-related gene expression, together with the upregulation of genes associated with interferon-γ responses and antigen presentation. Neuroinflammation in the cortex of mice and humans during acute GVHD was recently shown to be mediated by resident microglia-derived tumor necrosis factor. In contrast, infiltration of proinflammatory major histocompatibility complex (MHC) class II+ donor bone marrow (BM)-derived macrophages (BMDMs) was identified as a distinguishing feature of CNS cGVHD. Donor BMDMs, which composed up to 50% of the CNS myeloid population, exhibited a transcriptional signature distinct from resident microglia. Recipients of MHC class II knockout BM grafts exhibited attenuated neuroinflammation and behavior comparable to controls, suggestive of a critical role of donor BMDM MHC class II expression in CNS cGVHD. Our identification of disease mediators distinct from those in the acute phase indicates the necessity to pursue alternative therapeutic targets for late-stage neurological manifestations., (© 2022 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Background & Aims: Fibrosis, the primary cause of morbidity in chronic liver disease, is induced by pro-inflammatory cytokines, immune cell infiltrates, and tissue resident cells that drive excessive myofibroblast activation, collagen production, and tissue scarring. Rho-associated kinase 2 (ROCK2) regulates key pro-fibrotic pathways involved in both inflammatory reactions and altered extracellular matrix remodelling, implicating this pathway as a potential therapeutic target., Methods: We used the thioacetamide-induced liver fibrosis model to examine the efficacy of administration of the selective ROCK2 inhibitor KD025 to prevent or treat liver fibrosis and its impact on immune composition and function., Results: Prophylactic and therapeutic administration of KD025 effectively attenuated thioacetamide-induced liver fibrosis and promoted fibrotic regression. KD025 treatment inhibited liver macrophage tumour necrosis factor production and disrupted the macrophage niche within fibrotic septae. ROCK2 targeting in vitro directly regulated macrophage function through disruption of signal transducer and activator of transcription 3 (STAT3)/cofilin signalling pathways leading to the inhibition of pro-inflammatory cytokine production and macrophage migration. In vivo , KDO25 administration significantly reduced STAT3 phosphorylation and cofilin levels in the liver. Additionally, livers exhibited robust downregulation of immune cell infiltrates and diminished levels of retinoic acid receptor-related orphan receptor gamma (RORγt) and B-cell lymphoma 6 (Bcl6) transcription factors that correlated with a significant reduction in liver IL-17, splenic germinal centre numbers and serum IgG., Conclusions: As IL-17 and IgG-Fc binding promote pathogenic macrophage differentiation, together our data demonstrate that ROCK2 inhibition prevents and reverses liver fibrosis through direct and indirect effects on macrophage function and highlight the therapeutic potential of ROCK2 inhibition in liver fibrosis., Lay Summary: By using a clinic-ready small-molecule inhibitor, we demonstrate that selective ROCK2 inhibition prevents and reverses hepatic fibrosis through its pleiotropic effects on pro-inflammatory immune cell function. We show that ROCK2 mediates increased IL-17 production, antibody production, and macrophage dysregulation, which together drive fibrogenesis in a model of chemical-induced liver fibrosis. Therefore, in this study, we not only highlight the therapeutic potential of ROCK2 targeting in chronic liver disease but also provide previously undocumented insights into our understanding of cellular and molecular pathways driving the liver fibrosis pathology., Competing Interests: The authors declare no competing financial interests. BRB receives remuneration as an advisor to Magenta Therapeutics and BlueRock Therapeutics; received research funding from BlueRock Therapeutics, Rheos Medicines, Childrens' Cancer Research Fund, and KidsFirst Fund; and is a co-founder of Tmunity. MN, WC, and AZZ are full-time employees of Kadmon Pharmaceuticals, LLC. Please refer to the accompanying ICMJE disclosure forms for further details., (© 2021 The Authors.)

Regulatory T cell (Treg) reconstitution is essential for reestablishing tolerance and maintaining homeostasis following stem-cell transplantation. We previously reported that bone marrow (BM) is highly enriched in autophagy-dependent Treg and autophagy disruption leads to a significant Treg loss, particularly BM-Treg. To correct the known Treg deficiency observed in chronic graft-versus-host disease (cGVHD) patients, low dose IL-2 infusion has been administered, substantially increasing peripheral Treg (pTreg) numbers. However, as clinical responses were only seen in ∼50% of patients, we postulated that pTreg augmentation was more robust than for BM-Treg. We show that BM-Treg and pTreg have distinct characteristics, indicated by differential transcriptome expression for chemokine receptors, transcription factors, cell cycle control of replication and genes linked to Treg function. Further, BM-Treg were more quiescent, expressed lower FoxP3, were highly enriched for co-inhibitory markers and more profoundly depleted than splenic Treg in cGVHD mice. In vivo our data are consistent with the BM and not splenic microenvironment is, at least in part, driving this BM-Treg signature, as adoptively transferred splenic Treg that entered the BM niche acquired a BM-Treg phenotype. Analyses identified upregulated expression of IL-9R, IL-33R, and IL-7R in BM-Treg. Administration of the T cell produced cytokine IL-2 was required by splenic Treg expansion but had no impact on BM-Treg, whereas the converse was true for IL-9 administration. Plasmacytoid dendritic cells (pDCs) within the BM also may contribute to BM-Treg maintenance. Using pDC-specific BDCA2-DTR mice in which diptheria toxin administration results in global pDC depletion, we demonstrate that pDC depletion hampers BM, but not splenic, Treg homeostasis. Together, these data provide evidence that BM-Treg and splenic Treg are phenotypically and functionally distinct and influenced by niche-specific mediators that selectively support their respective Treg populations. The unique properties of BM-Treg should be considered for new therapies to reconstitute Treg and reestablish tolerance following SCT., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Nicholls, Cao, Le Texier, Xiong, Hunter, Llanes, Aguliar, Schroder, Phipps, Lynch, Cao, Heazlewood, Williams, Clouston, Nefzger, Polo, Nilsson, Blazar and MacDonald.)

Positive results from recent clinical trials have significantly expanded current therapeutic options for patients with chronic graft-versus-host disease (GVHD). However, new insights into the associations between clinical characteristics of chronic GVHD, pathophysiologic mechanisms of disease, and the clinical and biological effects of novel therapeutic agents are required to allow for a more individualized approach to treatment. The current report is focused on setting research priorities and direction in the treatment of chronic GVHD. Detailed correlative scientific studies should be conducted in the context of clinical trials to evaluate associations between clinical outcomes and the biological effect of systemic therapeutics. For patients who require systemic therapy but not urgent initiation of glucocorticoids, clinical trials for initial systemic treatment of chronic GVHD should investigate novel agents as monotherapy without concurrently starting glucocorticoids, to avoid confounding biological, pathological, and clinical assessments. Clinical trials for treatment-refractory disease should specifically target patients with incomplete or suboptimal responses to most recent therapy who are early in their disease course. Close collaboration between academic medical centers, medical societies, and industry is needed to support an individualized, biology-based strategic approach to chronic GVHD therapy., (Copyright © 2021 The American Society for Transplantation and Cellular Therapy. All rights reserved.)

Cardiac injury and dysfunction occur in COVID-19 patients and increase the risk of mortality. Causes are ill defined but could be through direct cardiac infection and/or inflammation-induced dysfunction. To identify mechanisms and cardio-protective drugs, we use a state-of-the-art pipeline combining human cardiac organoids with phosphoproteomics and single nuclei RNA sequencing. We identify an inflammatory "cytokine-storm", a cocktail of interferon gamma, interleukin 1β, and poly(I:C), induced diastolic dysfunction. Bromodomain-containing protein 4 is activated along with a viral response that is consistent in both human cardiac organoids (hCOs) and hearts of SARS-CoV-2-infected K18-hACE2 mice. Bromodomain and extraterminal family inhibitors (BETi) recover dysfunction in hCOs and completely prevent cardiac dysfunction and death in a mouse cytokine-storm model. Additionally, BETi decreases transcription of genes in the viral response, decreases ACE2 expression, and reduces SARS-CoV-2 infection of cardiomyocytes. Together, BETi, including the Food and Drug Administration (FDA) breakthrough designated drug, apabetalone, are promising candidates to prevent COVID-19 mediated cardiac damage., Competing Interests: Declaration of interests R.J.M., J.E.H., G.A.Q.-R., D.M.T., and E.R.P. are co-inventors on patents relating to cardiac organoid maturation and cardiac therapeutics. J.E.H. is co-inventor on licensed patents for engineered heart muscle. R.J.M., E.R.P., D.M.T., B.G., and J.E.H. are co-founders, scientific advisors, and stockholders in Dynomics. D.M.T. and B.G. are employees of Dynomics. C.H., D.G., L.F., J.J., M.S., N.C.W.W., and E.K. are employees of Resverlogix. S.J.N. received honoraria and research support from Resverlogix. QIMR Berghofer Medical Research Institute filed a patent on the use of BETi., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) is known to facilitate caspase-1 activation, which is essential for innate host immunity via the formation of the inflammasome complex, a multiprotein structure responsible for processing IL1β and IL18 into their active moieties. Here, we demonstrated that ASC-deficient CD8 + T cells failed to induce severe graft-versus-host disease (GVHD) and had impaired capacity for graft rejection and graft-versus-leukemia (GVL) activity. These effects were inflammasome independent because GVHD lethality was not altered in recipients of caspase-1/11-deficient T cells. We also demonstrated that ASC deficiency resulted in a decrease in cytolytic function, with a reduction in granzyme B secretion and CD107a expression by CD8 + T cells. Altogether, our findings highlight that ASC represents an attractive therapeutic target for improving outcomes of clinical transplantation., (©2020 American Association for Cancer Research.)

Cognitive dysfunction and reactive microglia are hallmarks of traumatic brain injury (TBI), yet whether these cells contribute to cognitive deficits and secondary inflammatory pathology remains poorly understood. Here, we show that removal of microglia from the mouse brain has little effect on the outcome of TBI, but inducing the turnover of these cells through either pharmacologic or genetic approaches can yield a neuroprotective microglial phenotype that profoundly aids recovery. The beneficial effects of these repopulating microglia are critically dependent on interleukin-6 (IL-6) trans-signaling via the soluble IL-6 receptor (IL-6R) and robustly support adult neurogenesis, specifically by augmenting the survival of newborn neurons that directly support cognitive function. We conclude that microglia in the mammalian brain can be manipulated to adopt a neuroprotective and pro-regenerative phenotype that can aid repair and alleviate the cognitive deficits arising from brain injury., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has recently emerged as an important pathogenic cytokine in acute graft-versus-host disease (GVHD), but the nature of the T-cell lineages secreting the cytokine and the mechanisms of action are less clear. Here we used interleukin 17A-fate reporter systems with transcriptional analysis and assays of alloantigen presentation to interrogate the origins of GM-CSF-secreting T cells and the effects of the cytokine on antigen-presenting cell (APC) function after experimental allogeneic stem cell transplantation (SCT). We demonstrated that although GM-CSF-secreting Th17 and non-Th17 cells expanded in the colon over time after SCT, the Th17 lineage expanded to represent 10% to 20% of the GM-CSF secreting T cells at this site by 4 weeks. Donor T-cell-derived GM-CSF expanded alloantigen-presenting donor dendritic cells (DCs) in the colon and lymph nodes. In the mesenteric lymph nodes, GM-CSF-dependent DCs primed donor T cells and amplified acute GVHD in the colon. We thus describe a feed-forward cascade whereby GM-CSF-secreting donor T cells accumulate and drive alloantigen presentation in the colon to amplify GVHD severity. GM-CSF inhibition may be a tractable clinical intervention to limit donor alloantigen presentation and GVHD in the lower gastrointestinal tract., (© 2019 by The American Society of Hematology.)

Hepatic fibrosis is the central cause of chronic clinical pathology resulting from infection by the blood flukes Schistosoma japonicum or S. mansoni. Much has been elucidated regarding the molecular, cellular and immunological responses that correspond to the formation of the granulomatous response to trapped schistosome eggs. A central feature of this Th2 response is the deposition of collagen around the periphery of the granuloma. To date, traditional histology and transcriptional methods have been used to quantify the deposition of collagen and to monitor the formation of the hepatic granuloma during experimental animal models of schistosomiasis. We have investigated the dynamic nature of granuloma formation through the use of a transgenic mouse model (B6.Collagen 1(A) luciferase mice (B6.Coll 1A-luc + )). With this model and whole-animal bioluminescence imaging, we followed the deposition of collagen during an active schistosome infection with Chinese and Philippines geographical strains of S. japonicum and after clearance of the adult parasites by the drug praziquantel. Individual mice were re-imaged over the time course to provide robust real-time quantitation of the development of chronic fibrotic disease. This model provides an improved method to follow the course of hepatic schistosomiasis-induced hepatic pathology and effectively supports the current dogma of the formation of hepatic fibrosis, originally elucidated from static traditional histology. This study demonstrates the first use of the B6.Coll 1A-luc + mouse to monitor the dynamics of disease development and the treatment of pathogen-induced infection with the underlying pathology of fibrosis.

Autologous stem cell transplantation (SCT) remains a standard of care for multiple myeloma (MM) patients and prolongs progression-free survival. A small cohort of patients achieve long-term control of disease, but the majority of patients ultimately relapse, and the mechanisms permitting disease progression remain unclear. In this study, we used a preclinical model of autologous SCT for myeloma where the disease either progressed (MM relapsed) or was controlled. In the bone marrow (BM), inhibitory receptor expression on CD8 + T cells correlated strongly with myeloma progression after transplant. In conjunction, the costimulatory/adhesion receptor CD226 (DNAM-1) was markedly downregulated. Interestingly, DNAM-1 - CD8 + T cells in MM-relapsed mice had an exhausted phenotype, characterized by upregulation of multiple inhibitory receptors, including T-cell immunoglobulin and ITIM domains (TIGIT) and programmed cell death protein 1 (PD-1) with decreased T-bet and increased eomesodermin expression. Immune checkpoint blockade using monoclonal antibodies against PD-1 or TIGIT significantly prolonged myeloma control after SCT. Furthermore, CD8 + T cells from MM-relapsed mice exhibited high interleukin-10 (IL-10) secretion that was associated with increased TIGIT and PD-1 expression. However, while donor-derived IL-10 inhibited myeloma control post-SCT, this was independent of IL-10 secretion by or signaling to T cells. Instead, the donor myeloid compartment, including colony-stimulating factor 1 receptor-dependent macrophages and an IL-10-secreting dendritic cell population in the BM, promoted myeloma progression. Our findings highlight PD-1 or TIGIT blockade in conjunction with SCT as a potent combination therapy in the treatment of myeloma., (© 2018 by The American Society of Hematology.)

Current approaches to prevent and treat graft-versus-host disease (GVHD) after stem cell transplantation rely principally on pharmacological immune suppression. Such approaches are limited by drug toxicity, nonspecific immune suppression, and a requirement for long-term therapy. Our increased understanding of the regulatory cells and molecular pathways involved in limiting pathogenic immune responses opens the opportunity for the use of these cell subsets to prevent and/or GVHD. The theoretical advantages of this approach is permanency of effect, potential for facilitating tissue repair, and induction of tolerance that obviates a need for ongoing drug therapy. To date, a number of potential cell subsets have been identified, including FoxP3 + regulatory T (Treg) and FoxP3 neg IL-10 + (FoxP3-negative) regulatory T (Tr1), natural killer (NK) and natural killer T (NKT) cells, innate lymphoid cells, and various myeloid suppressor populations of hematopoietic (eg, myeloid derived suppressor cells) and stromal origin (eg, mesenchymal stem cells). Despite initial technical challenges relating to large-scale selection and expansion, these regulatory lineages are now undergoing early phase clinical testing. To date, Treg therapies have shown promising results in preventing clinical GVHD when infused early after transplant. Results from ongoing studies over the next 5 years will delineate the most appropriate cell lineage, source (donor, host, third party), timing, and potential exogenous cytokine support needed to achieve the goal of clinical transplant tolerance., (© 2018 by The American Society of Hematology.)

Regulatory T cells (Tregs) are key mediators of the immune system. MicroRNAs (miRNAs) are a family of ~22 nucleotide non-coding RNAs that are processed from longer precursors by the RNases Drosha and Dicer. miRNA regulates protein expression posttranscriptionally through mRNA destabilization or translational silencing. A critical role for miRNA in Treg function was initially discovered when both Dicer and Drosha knockout (KO) mice were found to develop a fatal autoimmune disease phenotypically similar to Foxp3 KO mice.

The liver is positioned at the interface between two routes traversed by pathogens in disseminating infection. Whereas blood-borne pathogens are efficiently cleared in hepatic sinusoids by Kupffer cells (KCs), it is unknown how the liver prevents dissemination of peritoneal pathogens accessing its outer membrane. We report here that the hepatic capsule harbors a contiguous cellular network of liver-resident macrophages phenotypically distinct from KCs. These liver capsular macrophages (LCMs) were replenished in the steady state from blood monocytes, unlike KCs that are embryonically derived and self-renewing. LCM numbers increased after weaning in a microbiota-dependent process. LCMs sensed peritoneal bacteria and promoted neutrophil recruitment to the capsule, and their specific ablation resulted in decreased neutrophil recruitment and increased intrahepatic bacterial burden. Thus, the liver contains two separate and non-overlapping niches occupied by distinct resident macrophage populations mediating immunosurveillance at these two pathogen entry points to the liver., (Copyright © 2017 Elsevier Inc. All rights reserved.)

T-helper 17 (Th17) cells have been widely implicated as drivers of autoimmune disease. In particular, Th17 cytokine plasticity and acquisition of an interleukin-17A + (IL-17A + )interferon γ(IFNγ) + cytokine profile is associated with increased pathogenic capacity. Donor Th17 polarization is known to exacerbate graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT); however, donor Th17 cytokine coexpression and plasticity have not been fully characterized. Using IL-17 "fate-mapping" mice, we identified IL-6-dependent Th17 cells early after allo-SCT, characterized by elevated expression of proinflammatory cytokines, IL-17A, IL-22, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor. This population did not maintain lineage fidelity, with a marked loss of IL-17A and IL-22 expression late posttransplant. Th17 cells were further segregated based on IFNγ coexpression, and IL-17A + IFNγ + Th17 displayed an enhanced proinflammatory phenotype. Th17 cytokine plasticity and IFNγ production were critically dependent upon donor-derived IL-12p40, and cyclosporine (CsA) treatment regulated this differentiation pathway. This observation was highly concordant with clinical samples from allo-SCT recipients receiving CsA-based immune suppression where although the IFNγ-negative-Th17 subset predominated, IFNγ + -Th17 cells were also present. In sum, Th17 polarization and ensuing differentiation are mediated by sequential inflammatory signals, which are modulated by immunosuppressive therapy, leading to distinct phenotypes within this lineage., Competing Interests: Conflict-of-interest disclosure: G.R.H. has received funding from Roche Ltd for clinical trial studies and has served as a paid consult for Amgen Inc. The remaining authors declare no competing financial interests.

IL-17-producing helper T (Th17) cells are critical for host defense against extracellular pathogens but also drive numerous autoimmune diseases. Th17 cells that differ in their inflammatory potential have been described including IL-10-producing Th17 cells that are weak inducers of inflammation and highly inflammatory, IL-23-driven, GM-CSF/IFNγ-producing Th17 cells. However, their distinct developmental requirements, functions and trafficking mechanisms in vivo remain poorly understood. Here we identify a temporally regulated IL-23-dependent switch from CCR6 to CCR2 usage by developing Th17 cells that is critical for pathogenic Th17 cell-driven inflammation in experimental autoimmune encephalomyelitis (EAE). This switch defines a unique in vivo cell surface signature (CCR6(-)CCR2(+)) of GM-CSF/IFNγ-producing Th17 cells in EAE and experimental persistent extracellular bacterial infection, and in humans. Using this signature, we identify an IL-23/IL-1/IFNγ/TNFα/T-bet/Eomesodermin-driven circuit driving GM-CSF/IFNγ-producing Th17 cell formation in vivo. Thus, our data identify a unique cell surface signature, trafficking mechanism and T-cell intrinsic regulators of GM-CSF/IFNγ-producing Th17 cells.

Background: Interleukin 6 mediates graft-versus-host disease (GVHD) in experimental allogeneic stem-cell transplantation (allogeneic SCT) and represents an attractive therapeutic target. We aimed to assess whether the humanised anti-interleukin-6 receptor monoclonal antibody, tocilizumab, could attenuate the incidence of acute GVHD., Methods: We undertook a single-group, single-institution phase 1/2 study at the Royal Brisbane and Women's Hospital Bone Marrow Transplantation unit, QLD, Australia. Eligible patients were 18-65 years old and underwent T-replete HLA-matched allogeneic SCT with either total body irradiation-based myeloablative or reduced-intensity conditioning from unrelated or sibling donors. One intravenous dose of tocilizumab (8 mg/kg, capped at 800 mg, over 60 mins' infusion) was given the day before allogeneic SCT along with standard GVHD prophylaxis (cyclosporin [5 mg/kg per day on days -1 to +1, then 3 mg/kg per day to maintain therapeutic levels (trough levels of 140-300 ng/mL) for 100 days plus methotrexate [15 mg/m(2) on day 1, then 10 mg/m(2) on days 3, 6, and 11]). The primary endpoint was incidence of grade 2-4 acute GVHD at day 100, assessed and graded as per the Seattle criteria. Immunological profiles were compared with a non-randomised group of patients receiving allogeneic SCT, but not treated with tocilizumab. This trial is registered with the Australian and New Zealand Clinical Trials Registry, number ACTRN12612000726853., Findings: Between Jan 19, 2012, and Aug 27, 2013, 48 eligible patients receiving cyclosporin and methotrexate as GVHD prophylaxis were enrolled into the study. The incidence of grade 2-4 acute GVHD in patients treated with tocilizumab at day 100 was 12% (95% CI 5-24), and the incidence of grade 3-4 acute GVHD was 4% (1-13). Grade 2-4 acute GVHD involving the skin developed in five (10%) patients of 48 treated with tocilizumab, involving the gastrointestinal tract in four (8%) patients; there were no reported cases involving the liver. Low incidences of grade 2-4 acute GVHD were noted in patients receiving both myeloablative total body irradiation-based conditioning (12% [95% CI 2-34) and fludarabine and melphalan reduced-intensity conditioning (12% [4-27]). Immune reconstitution was preserved in recipients of interleukin-6 receptor inhibition, but qualitatively modified with suppression of known pathogenic STAT3-dependent pathways., Interpretation: Interleukin 6 is the main detectable and dysregulated cytokine secreted after allogeneic SCT and its inhibition is a potential new and simple strategy to protect from acute GVHD despite robust immune reconstitution; a randomised, controlled trial assessing tocilizumab in addition to standard GVHD prophylaxis in these patients is warranted., Funding: National Health and Medical Research Council and Queensland Health., (Copyright © 2014 Elsevier Ltd. All rights reserved.)